1. Field of the Invention
The present invention relates to a film forming method and a film forming apparatus for supplying a processing solution to a substrate to form a film of the processing solution on the front surface of the substrate.
2. Description of the Related Art
In processes of semiconductor device fabrication, a so-called multilayer interconnection process in which multilayered aluminum electrodes are formed on the front face of a semiconductor wafer (referred to as "a wafer" hereinafter), for example, is performed. An inter-level insulation film, for example, a polyimide film is formed between the aluminum electrodes.
It is required to form the polyimide film uniformly for preventing a drop in yield of products. The formation of the uniform polyimide film is also indispensable for the performance of uniform exposure processing, etching processing, and the like in the lithography process after the multilayer interconnection process. In forming the uniform polyimide film, a spin coating method, for instance, has been adopted so far. The spin coating method is a method in which a polyimide in liquid form is supplied to the front surface of a wafer, the wafer is then rotated, and that the polyimide on the wafer is diffused and applied by centrifugal force due to the rotation.
So-called side rinse processing in which a cleaner such as a solvent for polyimide (hereinafter referred to as "a solvent") is supplied to a peripheral edge portion of a wafer on which the polyimide film is formed by the spin coating method to remove the polyimide film at the peripheral edge portion of the wafer is conventionally performed, thereby preventing the polyimide film at the peripheral edge portion of the wafer from adhering to tweezers which support the peripheral edge portion of the wafer and contaminating the tweezers.
A polyimide film, however, has high fluidity, and thus the polyimide film on the side of the central portion of a wafer which has not dried yet sometimes flows out to the side of a peripheral edge portion of the wafer. Therefore, there arises a possibility that even though the aforesaid side rinse processing is performed, the polyimide which thereafter flows out to the side of the peripheral edge portion of the wafer adheres to the tweezers and contaminates them.
An object of the present invention is to provide a film forming method and a film forming apparatus which prevent a processing solution from flowing out to the peripheral edge portion and thus prevent a supporting member such as tweezers for supporting a substrate from being contaminated, even if a substrate is moved before the processing solution for forming a thin film completely dries after a thin film such as a polyimide film is formed.